Komatsu PC800SE-7 Fault Code E115: Complete Diagnostic Guide

What is Komatsu PC800SE-7 Fault Code E115?

Fault Code E115 indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the Engine Control Module (ECM). This code specifically relates to the temperature monitoring system that protects the Komatsu SAA6D140E-7 engine from overheating damage.

The coolant temperature sensor provides critical data to the ECM, which uses this information to adjust fuel injection timing, control engine speed, and activate warning systems. When E115 triggers, the ECM detects either an out-of-range voltage signal, an open/short circuit, or implausible temperature readings that don't correlate with actual operating conditions. For the PC800SE-7, this is particularly critical because improper temperature management can lead to severe engine damage, reduced hydraulic performance, and costly downtime on high-value used equipment.

Common Symptoms

• Engine warning light illuminated on the monitor panel with possible audible alarm
• Engine derate mode activated, limiting maximum RPM and hydraulic power output
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Difficulty starting in cold conditions or excessive white smoke during warm-up

Potential Causes

The most common technical causes for E115 on used PC800SE-7 excavators include:

• Coolant temperature sensor failure due to age-related degradation or internal element breakdown
• Wiring harness damage at known rub points near the engine block or along the frame rail where vibration causes insulation wear
• Corroded or loose connector pins at the sensor plug, especially on machines with high hour counts or exposure to harsh environments
• ECM internal fault affecting the temperature input circuit (less common but possible on older units)
• Low coolant level causing air pockets that affect sensor accuracy
• Ground circuit issues specific to the engine harness ground points

How to Troubleshoot and Fix Code E115

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block near the thermostat housing. Check for physical damage, coolant leaks, or corrosion on the connector terminals. On used excavators, pay special attention to harness routing where cables contact metal surfaces—this is a common failure point on the PC800SE-7.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At 20°C (68°F), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Check supply voltage at the harness connector with ignition on—you should see approximately 5 volts from the ECM. Test for continuity between the sensor ground and chassis ground.

Step 3: Circuit Verification Inspect the entire wiring harness from sensor to ECM for chafing, breaks, or shorts to ground. On high-hour used machines, remove protective loom and check for green corrosion on copper wires. Use Komatsu KOMTRAX or compatible diagnostic software to monitor live sensor data and compare against actual coolant temperature using an infrared thermometer.

Step 4: Component Replacement If sensor resistance is out of specification or wiring shows damage, replace the faulty component with genuine Komatsu parts to ensure proper ECM communication. After replacement, clear codes, run the engine through a complete heat cycle, and verify the code doesn't return.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnosis for complex electrical issues or if you're unfamiliar with heavy equipment systems.